Wholesaling is legal and legit all states besides Illinois. There are different aspects in certain states and sometimes counties as to how and what can be done without a license. If you are looking to learn you should go to a local REI or find someone on social media doing it in your local area.
Honestly the best thing about wholesaling is that it makes you look for and know how to find deals. But it is definitely a high paying job, if done correctly. My advice to anyone looking to get into real estate though creative finance would be to learn subject to as an acquisition. It takes you from being able to help only people with equity to truly being able to help everyone who is looking to sell.
You don't need a course to learn this strategy. There is a book called, "The Turn Key Investor" Subject to Handbook. Read that and follow Grant Kemp from Texas and Pace Morby from Arizona. These two are currently in the game and actually show and teach you about the strategy via YouTube. Pace has the more creative exit strategies of the two but they both are really good at helping people to understand.
And to answer the last part of your question decisively, traditional wholesaling is dead. The barrier to entry (or lack there of), the flood of weekend seminar warriors all saying the same thing, and the fact that a seller could list there house on the market and get above asking price in less than a week, all spell out the death of traditional wholesaling.
Unless you have the money to give it system, processes and a team you could be the next sob story on YouTube about how some guru swindled you out of your money. So wholesaling is good just not as a strategy on it's on.